III-nitride semiconductors formed from compounds in which N is combined with Al, Ga, In, or the like have conventionally been used as materials for ultraviolet light-emitting devices. III-nitride semiconductors made of high-Al-content AlGaN are particularly used for ultraviolet light-emitting devices or deep ultraviolet light light-emitting devices (DUV-LED) emitting light at a wavelength of 300 nm or less.
Examples of the characteristics required of a III-nitride semiconductor light-emitting device include high external quantum efficiency characteristics and low resistance characteristics. The applicant proposes in JP 2010-161311 A (PTL 1) that a layer serving as an energy barrier for electrons, which is called an electron blocking layer, is formed between a light emitting layer having a quantum well structure and a p-type cladding layer, thereby improving the light emission efficiency. The electron blocking layer serves as a barrier against a quantum well layer of a light emitting layer and prevents electrons from flowing excessively; thus, the efficiency of carrier injection can be improved.
Further, JP 2000-151023 A (PTL 2) discloses a semiconductor light-emitting device using a nitride-based compound semiconductor, in which a heavily doped layer having locally been doped at a concentration higher than that for the whole p-type cladding layer is provided in a p-type cladding layer on the p-side light guide layer boundary side. According to PTL 2, the provision of the heavily doped layer having locally been doped at a concentration higher than that for the whole p-type cladding layer in part of the p-type cladding layer leads to increased hole concentration without reducing the crystallinity of the p-type cladding layer, thereby reducing the series resistance to lower the threshold current density.